External Slip Wall
Use the External Slip Wall node to specify a wall with slip when the adjacent wall is external to the whole geometry. The wall temperature, wall velocity, and slip coefficients are specified.
Slip Wall
Enter the components for the Velocity of moving wall uw.
Enter a value or expression for the Wall temperature Tw. The default is 293.15 K.
Select the Slip coefficients: Maxwell’s model (the default) or User defined.
Maxwell’s Model
For Maxwell’s Model enter values or expressions for the Tangential momentum accommodation coefficient av. The tangential accommodation coefficients are typically in the range of 0.85 to 1.0 and can be found in Ref. 4.
User defined
For User defined select a Mean free path definition — Standard (the default) or Alternative (Sharipov). Then enter values for the following. Note that the defaults are different based on the Mean free path definition chosen.
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Thermal slip coefficient σT. The defaults are 1.2 for Standard and 1.1 for Alternative (Sharipov).
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Viscous slip coefficient σS. The defaults are 1.1 for Standard and 1 for Alternative (Sharipov).
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Temperature jump coefficient ζT. The defaults are 2.2 for Standard and 1.95 for Alternative (Sharipov).
Theoretical and experimental values of these coefficients for various gas surface combinations are available in Ref. 5. Note that it is more convenient to use the Alternative (Sharipov) mean free path definition when using this data.